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Saturday, November 03, 2007

For the Physics Guys

Newton's Bit does a terrific job of analyzing the kinetic energy released by the Twin Towers and reveals that there is sufficient energy for the pulverization, unlike the claims of Gordon Ross:

The “pulvierisation” of concrete is perhaps the biggest flaw in Ross’ paper. He lists a total of 608MJ lost from this event. In reality, the loss of kinetic energy due to pulverized concrete is ZERO MJ. Why is this? It’s already been accounted for. Recall that the loss of kinetic energy from an inelastic collision. This means that some of the kinetic energy is converted into heat, some into sound and the vast majority into strain energy. The strain energy category includes this pulverized concrete. In reality, core columns punching through the floor slabs, or concrete debris doing the same, would cause an additional amount of interal energy to be added into the concrete slabs. However the Ross model only allows the columns to land directly on top of each other, as this is most conservative to collapse prevention.

A question might still remain for some readers as to why so much of the concrete in the tower was turned into a fine particulate dust. The answer to that question lies not in the impact of one floor against another floor, but in the eventual impact of the entire structure into the ground. At that point, almost all of the available kinetic energy will be converted into internal energies. Again, some into heat, some into sound, but the vast majority into strain energy.

Terrific analysis. The JREF Forum has an amazing number of extremely smart people.